What size lawn mower blade adaptor fit the predator 173 cc engine shaft?

Blade adapter from a MTD or Yard Machine seemed to fit the keyed shaft. Center bolt is 3/8" with 24 threads per inch. My issue is the shaft on the Predator is 1/2" longer than my original Yard machine, Briggs and Straton. So I either need to cut the shaft off, or raise the motor on a half inch thick spacer plate to get the blade at the same height it was on the original motor.